If you're a runner than you probably think that stretching is an important part of staying healthy and, as a longtime running coach, I would agree. But the type of stretching that you do is of vital importance. I'm a huge fan of a type of stretching called Active Isolated Flexibility (AIF), which has been popularized in the running world by Jim and Phil Wharton.
Olympic medalist and 2014 Boston Marathon champion Meb Keflezighi has used AIF to stay healthy while running high mileage, but so have high school freshmen and masters runners. AIF is easy to learn and it only takes 10 to 15 minutes to complete a well-rounded routine.
What Is Active Isolated Flexibility?
AIF is not static stretching, or bending over and touching your toes and holding that position for 10 to 20 seconds. AIF employs a rope (or you could use a towel or a dog leash or whatever works) to help you assist the body at the end of the range of motion of the stretch. The muscles in the body work in pairs. If you want to lengthen the hamstring and improve your hamstring flexibility, then you should contract the quadriceps muscle to help this process. It's that simple: Contract one muscle to lengthen the other muscle. This is where the "active" in AIF comes in—you have to activate a muscle group to lengthen the opposing muscle group.
Complete between eight and 10 reps of each exercise. Work into the range of motion of each exercise: your first two reps should be nice and gentle, yet by the eighth or ninth rep, you should be able go a little farther. Just remember that going farther is not the goal; rather, going just to the end of your range of motion is the goal.
The breathing component is key to practicing AIF correctly: Exhale when you lengthen the muscle, and inhale as you let the muscle contract slowly. This simple breathing pattern relieves stress in a way that's similar to yoga or meditation.
While some people do their AIF in front a TV, I ask my athletes to do it without any noise a couple of times a week so they can tune in to their breathing. Practice this inhale-exhale breathing pattern a few times without distraction and, once you're breathing properly during the movements, you can practice AIF in front of the TV.
The following video of Phil Wharton demonstrating a hamstring exercise illustrates the fundamentals of AIF.
Phil mentioned much of this in the video, but here's a summary of the hamstring exercise. While at first glance it looks like you're pulling on the top of the rope to stretch the hamstring, nothing could be further from the truth. Look at the slack in the rope when Phil begins to bring his leg off of the table. That slack means that it's his leg doing the work, not the rope. Specifically, Phil is contracting his quadriceps muscle to lift his leg off of the table. At the very top of the movement, Phil uses the rope to "assist" with getting a degree or two more added to his range of motion. But it's an "assist" and not a "pull." As you can see, the use of the rope is the key to doing AIF correctly—you use your muscles at the start of the move, and don't use the rope until the end of the of the move to extend the range of motion a bit more.